The invention relates to a method for operating an internal combustion engine with direct fuel injection, in particular a spark-ignited internal combustion engine with direct fuel injection.
In the operation of new internal combustion engines with direct fuel injection, improvements in the mixture formation by the configuration of the fuel injection profile are obtained both for self-igniting and for spark-ignited internal combustion engines. It is attempted to influence the combustion and the emission formation by varying the shape of the fuel injection profile.
DE 198 57 785 C2 discloses a method for the formation of a fuel mixture in a combustion chamber of an internal combustion engine, in which the fuel is injected in three stages, in which a main quantity of fuel is joined with an ignition quantity of fuel via an additional quantity of fuel without the injection being interrupted. With the additional quantity of fuel, which is injected between the main quantity injection of fuel and the igniting quantity injection of fuel, the times of the beginning and end of the injections of the main quantity of fuel and of the additional igniting quantity of fuel can be selected in a flexible manner.
DE 100 40 117 A1 discloses a method for operating a diesel engine, in which it is attempted, by particularly rapidly opening an injector valve, to achieve good homogenization of the fuel/air mixture. In this method, a sharp injection profile is obtained by the sudden opening of the injector valve in order to improve the homogenization of the fuel/air mixture.
Furthermore, DE 100 12 970 A1 discloses a method for forming an ignitable fuel/air mixture, in which the fuel is introduced in at least two partial quantities into the combustion space of the internal combustion engine, wherein the body of an injection nozzle can be brought into its closed position after a partial quantity of fuel is injected. The fuel beam is accelerated in the nozzle up to the outlet by the fact that the nozzle opening continuously narrows toward the outlet with a curved or parabola-shaped discharging passage.
DE 19636088 discloses a method for controlling the direct injection of fuel into the combustion space of an internal combustion engine, with which different fuel flow control cross-sections are obtained by means of a stroke-dependent, actuator, so that, in the case of temporally consecutive valve positions between the beginning and the end of the injection process, the fuel flow control cross-section of a control valve always remains above a minimum value which is different from the closed position.
The publication DE 19642653 C1 discloses a method for the mixture formation of an internal combustion engine with direct fuel injection, with which, during the injection of fuel, an opening stroke of a valve element relative to a valve seat of an injector and the injection time can be variably adjusted, for thus dynamically influencing the injection angle and also the mass flow of fuel.
Since as a result of manufacturing tolerances different fuel jets are generated, which often lead to spark failures because of different mixture formations the particular geometry of the injection nozzles would have to be corrected before they are installed in an internal combustion engine, which is practically impossible.
It is therefore the object of the invention to provide an injection nozzle whereby an optimum injection behavior and consequently an improved combustion can be obtained despite manufacturing tolerances.